The present invention concerns a device for temporarily storing volatile fuel constituents and supplying them at a controlled rate to the intake pipe of an internal combustion engine, wherein a shut-off valve is accommodated in a line that extends through a volatile fuel absorber to the intake pipe of an engine.
A device of this type is known from the German Patent No. 3,802,664 and the U.S. Pat. No. 4,901,702. The device is intended to prevent the volatile fuel constituents, always present in the empty space at the top of an internal combustion engine's fuel tank, from escaping into the atmosphere. The device comprises a special venting line between this space and the atmosphere which accommodates a reservoir containing a volatile fuel absorber. The absorber usually comprises a permeable mass of activated carbon that can temporarily store a considerable volume of volatile fuel. The absorber is regenerated by forcing fresh air through it while the engine is operating normally. The device therefore also comprises a line that connects the reservoir with the engine's intake pipe. It is also known to control the mass flow through this line leading to an internal combustion engine's intake pipe by means of one or more valves. An auxiliary valve is interposed directly upstream of a shut-off valve. The auxiliary valve can be closed off by a vacuum-controlled regulator governed by the difference between the pressure in a control chamber and atmospheric pressure.
It should be emphasized that controlling the rate at which volatile constituents are supplied to the intake pipe of an internal combustion engine is of significant importance. It is a prerequisite to unrestricted exploitation of the advantages of such a device. When problems with mass flow occur in a device of this type, which device comprises many individual components, it is impossible to detect and correct them. A malfunction on the part of the device has a negative effect on the environment due to the creation of engine exhaust pollutants. Uncombusted hydrocarbons can escape into the atmosphere as a result of a defective line without being noticed by those operating the internal combustion engine. The efficiency of the engine can also be affected negatively by malfunctions on the part of the device, especially in the form of rough engine operation.